Oil production from bituminous sand involves the basic steps of mining, bitumen extraction, bitumen froth treatment, and upgrading the bitumen to synthetic oil. Bitumen is commonly recovered from the surface-mined oil sands ore using a variation of the Clark Hot Water Extraction (CHWE) process. In this process, the ores are mined and then crushed for size reduction. Hot water is added to the ore to form a slurry, which is transported using a hydro-transport line to a primary separation vessel (PSV). Bitumen is recovered in the PSV by flotation of bitumen froth. The recovered bitumen froth may consist of about 60% bitumen, 10% solids and 30% water (by weight). The tailings materials from the PSV can be processed in a secondary flotation process to produce a secondary bitumen froth. The recovered bitumen froth can be sent to froth treatment vessels to reduce the water and solids content. Diluents (naphtha or paraffin solvents) are added and the diluted froth is heated to reduce the viscosity. At the end of the process, a mixture of clays, water, sand, and traces of unrecovered hydrocarbons combined with process chemicals, known as tailings, is pumped out to settling ponds and the recovered bitumen is sent to the upgrader.
Prior to the bitumen extraction process, and particularly prior to the recovery of bitumen by flotation, it is important that the oil sand feedstock be characterized and operating parameters be adjusted and controlled such that the percentage of bitumen recovered in the primary and secondary bitumen froths, and the quality of the recovered bitumen froths in terms of high bitumen, low water, and low solids content, is controlled within certain predetermined limits.
To achieve these goals, it is important to be able to measure the bitumen, water, and/or solids content in oil sand core samples in the laboratory, to help with mine planning, and oil sand ore samples on a conveyor belt, to monitor the feed material to help control the extraction process. It may also be important to be able to predict properties relating to the extraction characteristics (i.e. processability) of oil sand ores. As known in the art, Batch Extraction Units (BEU) [Sanford, E. C., Seyer, F. A., “Processability of Athabasca Tar Sand Using A Batch Extraction Unit: The Role of NaOH,” Canadian Mining & Metallurgical Bulletin (CIM Magazine), Vol. 72, Issue 803, March 1979, 164-169.] can be used to measure the extraction characteristics of oil sand ore samples under different conditions in order to better understand process conditions and sample properties that result in high bitumen recovery and high bitumen froth quality.
Several processes in the oil sands production may benefit from online monitoring. However, oil sand ore samples often present difficulties, largely related to the heterogeneity of the samples, different particle sizes, several phases, wetted and covered particles, and the fact that surface composition may not be representative of the bulk composition.
The Dean-Stark extraction method is considered to be an accurate method for determining bitumen, water, and/or solids content of a sample. A weighed sample is separated into bitumen, water, and solids by refluxing toluene in a Soxhlet extraction apparatus. Condensed toluene and co-distilled water are continuously separated in a trap designed to recycle the solvent through the extraction thimble, dissolving the bitumen present in the sample, while the water is retained in the trap. Full extraction of bitumen from the solids can often take hours to complete. Once the three components have been physically separated, they can be quantified by various means. The clean and dry solids can be further analyzed by a variety of techniques, including particle size distribution by wet sieving or laser diffraction, methylene blue index titration, elemental analysis, and mineralogy by X-ray diffraction.
Given the long analysis time of Dean-Stark extraction, and the inability to perform many other conventional laboratory measurements on the solids without first removing the bitumen and water, faster laboratory methods are often used to monitor a continuous extraction train used for extracting bitumen from oil sand. These fast methods typically sacrifice accuracy and/or repeatability in order to achieve a shorter analysis time. They often rely on an extraction step, filtration step, centrifugation step, and/or drying step to separate various components prior to measurement, which adds to the total analysis time. Extraction process conditions can quickly change within minutes, making ever shorter analysis times desirable. Many laboratory measurements cannot be performed sufficiently fast either online or in a laboratory setting to be useful for monitoring an extraction process (e.g. methylene blue index titration, elemental analysis, X-ray diffraction, and BEU extraction processability characteristics).
Nuclear magnetic resonance (NMR) techniques for measuring bitumen, water, and solids (by-difference) are known but are limited in the type of information that they can provide, as known to those skilled in the art.
Near-infrared reflectance measurements and 40K radiation measurements have been used to estimate the oil sand ore bitumen and fine particle content online. While efforts continue to improve the accuracy, precision, and reliability of these tools, they also provide only limited information about the ore as known to those skilled in the art.
Therefore, there remains a need in the art for analytical methods which may permit online, real-time monitoring of oil sand composition and extraction characteristics. Preferably, the method may be faster for measuring the content of bitumen, water and solids, compared to Dean-Stark extraction, while maintaining satisfactory accuracy and precision. The method may also provide additional information about the samples that cannot be measured quickly (e.g. minutes) in a laboratory or online using conventional analytical techniques.